The EChO spacecraft will have a launch mass of about 2.1 tons, and will be made up of two principle modules:
An ESA study carried out at the Concurrent Design Facility in ESTEC, the Netherlands, has provided a reference design concept for the primary payload elements: a simple Cassegrain telescope with a field-of-view of 20"x20", and a spectrometer covering the 0.4 – 11 micron waveband. This reference design will be studied further studied by ESA, while industry and instrument consortia will study and propose alternative designs over the next few months
The service module handles all functions needed to operate the payload, including the telemetry, power systems, thermal control and the attitude and orbit control systems (AOCS).
High photometric stability is one of the most stringent requirements of the EChO mission, with a stability of 10-4 (3 sigma) or better required over a time scale of about 10 hours. As a result, fine pointing stability relative to the host star is mandatory. This will be achieved with a combination of a fine guidance sensor (FGS) that uses a fraction of the signal from the optical channel, and fine AOCS actuators.